A Cincinnati-area businessman on Saturday offered a $25,000 reward for information leading to a suspect or suspects in the execution-style killings of eight members of the same family who were shot dead in four homes on Friday.
Ohio investigators worked through the night without making an arrest, officials said on Saturday.
The Ohio Bureau of Criminal Investigation and local law enforcement interviewed witnesses and executed search warrants overnight, according to a joint statement by the Ohio attorney general and the Pike County sheriff.
Photos from the scene:
"The investigation is still in its early stages, and no arrests have been made," the statement said.
Jeff Ruby, the owner of high-end steakhouses, has offered $25,000 for information that leads to the arrest and conviction of the person or people responsible, officials said in a later news release.
Investigators have yet to disclose a suspected motive in the massacre of the Rhoden family in Pike County, in the Appalachian region of south-central Ohio.
The victims included seven adults and one juvenile, all shot in the head, including the mother of a days-old infant.
The baby, a 6-month-old and a 3-year-old all survived the shootings. The mother of the newborn was in bed with her baby when she was killed, the Cincinnati Enquirer reported.
"That's heartless," Phil Fulton, pastor of the Union Hill Church in Peebles, the town where the shootings took place, told CNN. "I can't believe how anyone could kill a mother with her four-day-old baby in her arms."
Officials released recordings of two phone calls from people reporting killings at separate locations to the Pike County Sheriff's Office.
"There's blood all over the house. My brother-in-law's in the bedroom. It looks like someone has beat the hell out of him," says one distressed woman, who then reported seeing another body on the floor.
"I think they're both dead," she says.
In another call, a man calmly asks for a deputy.
"I just found my cousin with a gunshot wound," he says.
"Is he still alive?" asks the operator.
"No," the man responds.
Ohio Attorney General Mike DeWine said on Friday he was unsure if there was one perpetrator or more. None of the victims committed suicide, officials said.
"Reports we are receiving from Peebles are tragic beyond comprehension," Ohio governor and Republican presidential hopeful John Kasich said on Twitter. "We'll continue to monitor this closely and the state will work with local law enforcement however we can."